Recently, for lowering the resistance of an electrode material for a semiconductor device such as MOSFET, use of a nickel silicide film (NiSi) that is obtained by silicidation of a nickel thin film is contemplated. A method for formation of a NiSi film generally includes formation of a Ni thin film on a Si substrate and diffusing Si from the Si substrate by heat treatment of the film for silicidation and production of NiSi.
As described above, as a method for producing a Ni thin film to produce a NiSi thin film on a Si substrate, a physical vapor deposition (PVD) method such as sputtering was applied in many cases. However, an application of a chemical vapor deposition method such as a chemical vapor phase deposition method (CVD method) or an atomic layer deposition method (ALD method) currently receives attention. Recently, three-dimensional integration of a semiconductor device is under progress, and a stereo structure is employed for an electrode used for the three-dimensional integration. Additionally, since formation of a thin film with a stereo structure by a PVD method is difficult, application of the chemical vapor deposition method with excellent step coverage is preferable.
A method for producing a Ni film on a Si substrate by chemical vapor deposition in which nickel amidinate is basically used as a precursor (i.e., raw material compound) and NH3 is used as a reaction gas is known (Patent Document 1). The Ni film produced by application of nickel amidinate has nitrogen (N) derived from a raw material or N derived from NH3 as a reaction gas introduced in the film so that nickel nitride (NiNx) is produced in the film. Such impurities are an obstructive factor to low resistance of an electrode, in Patent Document 1, however they are subjected to heat treatment after film formation to remove N. In the aforementioned formation of a Ni thin film and process for increasing the purity, a Ni thin film with high purity, i.e., free of any N component, and low resistance can be finally formed. When this Ni thin film with high purity is formed on a Si substrate, a NiSi film can also be produced.
However, in the method involved with formation of a NiNx film, a decrease in film density or a change in shape (roughness) of a film occurs in accordance with removal of N, and presence of residual N is also concerned. Accordingly, there is a problem that a Ni thin film having high resistance compared to bulk Ni is yielded. Even when such a Ni thin film is silicidated, a desired electrode cannot be formed.
To form a high-quality Ni thin film with no residual impurities, it will be an appropriate approach to exclude an element like N possibly remaining in a Ni thin film as a constituent element for the precursor and reaction gas. As a preferred condition which may be considered from such point of view, a hydrocarbon-type Ni complex is preferably used as a precursor and hydrogen is employed as a reaction gas, because, with a use of the hydrocarbon-type Ni complex, complex components are released in the form of hydrocarbon so that residual impurities are less likely to be present in a thin film.